Mongo Shell and Commands

What is Mongo Shell?

Mongo Shell is a JavaScript-based interactive interface for MongoDB. It can execute any MongoDB-related query or command. After configuring the MongoDB environment variables, use the command Mongo to launch Mongo Shell.

Features of Mongo Shell

• Interactive JavaScript Environment: Use JavaScript to interact with databases, collections, and documents.
• CRUD Operations: You can create, read, update, and delete data directly from the shell.
• Aggregation Framework Support: Execute complicated data aggregation processes.
• Index Management: Create, drop, and maintain indexes to improve query performance.
• Administration Commands: Control instances, databases, and collections.
• JavaScript Expressions: Perform complex data manipulation and scripting.
• Scripting support: Create JavaScript scripts for automation and batch processing.
• Data Import and Export: You can import and export data in numerous formats using utility commands.
• Authentication and authorization: Use authentication procedures to ensure secure access.
• Replica Set and Sharding Operations: Manage replica sets and sharded clusters.
• Session Management: Keep sessions for many commands without re-authenticating.
• Tab completion & syntax highlighting: Improve the user experience and productivity.

Mongo Shell Commands

Start-up and Connection Commands

• mongod: Starts a local MongoDB server.
• mongo: Starts the MongoDB shell and connects to the default database, 'test'.
• Mongo <host_name>:<port>/<database_name> -U <username> -p <password> connects to a MongoDB server with authentication.
• mongo -version: Shows the version of the MongoDB shell.
• Mongo --nodb: Starts the MongoDB shell without connecting to a database.
• mongo <db_name>: Starts the MongoDB shell & connects to a specific database.

Basic Shell Commands

• help: Displays help for the current context or the MongoDB shell.
• Exit: Closes the MongoDB shell.
• db: Displays the currently selected database.
• Use <db_name>: Switches to and utilizes the specified database.
• show dbs: This command lists all available databases on the MongoDB server.
• Show collections: Shows all collections in the current database.
• Show users: Lists all of the users in the current database.

Document Commands

• db.users.insert: Adds a document to the 'users' collection.
• db.users.find: Returns documents from the 'users' collection depending on the query criteria.
• db.users.find().pretty: Returns documents from the 'users' collection in formatted output.
• db.users.findOne: Returns a single document from the 'users' collection based on the query parameters.
• db.users.find({ },{ name:true, _id:false }): Returns particular fields from documents in the 'users' collection.

Query operators

• db.users.find({"_id": {$gt: 1}}): Returns documents in the 'users' collection with a _id value greater than 1. 
• db.users.find({"_id": {$gte: 5}}): Returns documents in the 'users' collection with a _id value higher than or equal to 5. 
• db.users.find({"_id": {$lt: 1}}): Returns documents in the 'users' collection with a _id value less than 1. 
• db.users.find({"_id": {$lte: 5}}): Returns documents in the 'users' collection with a _id attribute less than or equal to 5. 
• db.users.find({"_id": {$in: [1,2,3]}}): Identifies documents in the 'users' collection whose _id attribute matches any value in the specified array.